A chemolithoautotroph is an autotrophic microorganism that obtains energy by oxidizing inorganic compounds. Most chemolithotrophs are autotrophs. Examples of relevant inorganic electron donors include hydrogen, hydrogen sulfide, ferrous iron, and ammonia. Winogradsky described the concept of chemolithoautotrophy for the first time while studying the ammonia-oxidizing bacteria. Chemolithoautotrophic organisms have electron transport complexes, similar to those of chemoorganotrophs, which are used to generate a protein motive force. The proton motive force drives the synthesis of ATP. In this case, the reduction of CO2requires the use of ATP and reducing power, which is, most often, obtained through the use of the electron transport chain in reverse mode, consuming energy. Sulfur, iron, and ammonia oxidizers are fundamental elements in the biogeochemical cycles of these elements....